Ishihara Test

Ishihara Test

Eye colour blindness is a condition that some have where they can’t tell certain colours apart, usually between red and green, and occasionally blue. There is a test that people take to see whether they have this colour deficiency or not, called the Ishihara Test. A Japanese professor called Dr Shinobu Ishihara was tasked with the job of creating the test for soldiers, which he did in 1917.

Facts About Colour Blindness

Colour blindness occurs in males, rarely in females, because the genes carrying the condition are in the X chromosome. Since women have two of these, a defect in one is compensated for in the other. The Ishihara test that is used, basically consists of a number of coloured plates which have a circle of dots that appear random in size and colour. Some of the dots form a pattern of numbers visible only to people with normal colour vision.

Colour Blindness Types

There are two types of colour blindness present, total and partial. Total colour deficiency makes people see everything in shades of black and white but is rare. In partial, the red-green eye colour deficiency, also called daltonism, is the most common type. People who suffer from this can’t tell different shades of red and green apart. It is usually self-diagnosed.

Colour Blindness Summary

As stated above, eye colour deficiency is a hereditary condition, found in about 8% of men and 0.5% of women around the World. It has no cure and can only be given minor treatment or tested. The Ishihara test is used to determine colour blindness and continues to use the method designed by Dr, Ishihara. This conclusively determines which type of colour blindness the person has, the most common type found is the red-green colour deficiency.